This invention relates to potentiometer assemblies, and more particularly to a novel potentiometer assembly suitable for producing tuning voltages for use with electronic tuners of television receivers and the like.
For many years, mechanical turret tuners have been commonly employed in television receivers to select the VHF channels, and a second rotary or continuous tuner has been used to select the UHF channels. For most television receivers, this requires two different channel selection knobs; and the tuners themselves are relatively bulky and require a relatively large amount of space within the television receiver cabinet. Because of the nature of these tuners, it also is necessary to locate them directly behind the front panel of the receiver cabinet. This imposes significant restrictions on the cabinet design and the arrangement of parts within the cabinet. As a consequence, design flexibility in the arrangement of the parts in the television chassis is considerably restricted.
Some mechanical tuners are equipped with programmable switches to permit them to be used to select either a UHF or a VHF channel at a tuner position by programming the tuner for the local area where the television receiver is to be used. The disadvantages of the cumbersome mechanical tuners are not overcome by such programmable arrangements, however. Instead, the tuner is made even more complicated.
It is desirable, and in the United States it is becoming necessary, to effect selection of the UHF and VHF channels in a comparable manner. When such tuning compatibility is imposed, significant problems are encountered in a mechanical turret-type tuner having detented positions for accommodating the VHF channels and all of the possible UHF channels which a receiver is capable of receiving in any given locality in which it is operated.
The introduction of voltage variable capacitor or varactor tuners for the VHF and UHF bands to which a television receiver can be tuned has opened the way for electronic tuning of television receivers. This permits replacement of the cumbersome mechanical turret tuners with arrangements which permit greater flexibility in the design of the channel selection panel and in the location of the various tuner parts within the receiver cabinet. If the receiver, however, is to be made capable of individual selection of a large number of the 70 UHF channels in addition to the VHF channels, it has been necessary to provide a large number of individual tuning components. For example, in many prior art electronic tuner control circuits, it has been necessary to provide a separate tuning potentiometer for each of the UHF channels and each of the VHF channels to which the receiver can be tuned. This results in a relatively expensive tuner configuration requiring a large number of parts.
It is desirable to provide a television tuning control system which is capable of tuning to any channel which the receiver can receive with equal ease of selection of VHF or UHF channels. In addition, it is desirable to provide a tuner control system which uses a minimum number of parts, facilitates fine tuning adjustments, which is compact in size, and is relatively inexpensive.